John Rawls shares the Enlightenment’s commitment to finding moral and political principles which can be reflectively endorsed by all individuals autonomously. He usually presents reflective autonomy in Kantian, rationalist terms: autonomy is identified with the exercise of reason, and principles of justice must be constructed which are acceptable to all on the basis of reason alone. Yet David Hume, Adam Smith and many other Enlightenment thinkers rejected such rationalism, searching instead for principles which can be endorsed by all on the basis of all the faculties of the human psyche, emotion and imagination included. The influence of these sentimentalists on Rawls is clearest in his descriptive moral psychology, but I argue that it is also present in Rawls’s understanding of the sources of normativity. Although this debt is obscured by Rawls’s explicit “Kantianism,” his theory would be strengthened by a greater understanding of its debts to the sentimentalist Enlightenment.